U.S. patent number 6,047,556 [Application Number 08/986,447] was granted by the patent office on 2000-04-11 for pulsed flow for capacity control.
This patent grant is currently assigned to Carrier Corporation. Invention is credited to Alexander Lifson.
United States Patent |
6,047,556 |
Lifson |
April 11, 2000 |
Pulsed flow for capacity control
Abstract
Step control in capacity modulation of a refrigeration or air
conditioning circuit is achieved by rapidly cycling a solenoid
valve in the suction line, economizer circuit or in a bypass with
the percent of "open" time for the valve regulating the rate of
flow therethrough. A common port in the compressor is used for
economizer flow and for bypass.
Inventors: |
Lifson; Alexander (Manlius,
NY) |
Assignee: |
Carrier Corporation (Syracuse,
NY)
|
Family
ID: |
25532427 |
Appl.
No.: |
08/986,447 |
Filed: |
December 8, 1997 |
Current U.S.
Class: |
62/196.2;
251/129.05; 62/196.4; 62/217; 62/513 |
Current CPC
Class: |
F25B
40/02 (20130101); F25B 41/22 (20210101); F25B
2400/13 (20130101); F25B 2600/2509 (20130101); F25B
2600/2521 (20130101) |
Current International
Class: |
F25B
41/04 (20060101); F25B 40/02 (20060101); F25B
40/00 (20060101); F25B 003/00 () |
Field of
Search: |
;62/196.2-196.4,217,513
;251/129.05 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bennett; Henry
Assistant Examiner: Norman; Marc
Claims
What is claimed is:
1. In a system serially including a compressor, a discharge line, a
condenser, an expansion device, an evaporator and a suction line,
means for achieving capacity control comprising:
a solenoid valve in said suction line;
means for rapidly pulsing said solenoid valve whereby the rate of
flow in said suction line to said compressor is modulated;
a fluid path extending from a point intermediate said condenser and
said expansion device to said compressor at a location
corresponding to an intermediate point of compression in said
compressor;
a bypass line connected to said fluid path and said suction
line;
a solenoid valve in said bypass line;
means for rapidly pulsing said solenoid valve in said bypass line
whereby the rate of flow of bypass to said suction line is
modulated.
2. The capacity control of claim 1 further including;
an economizer circuit connected to said fluid path;
a solenoid valve in said economizer circuit; and
means for rapidly pulsing said solenoid valve in said economizer
circuit whereby the rate of economizer flow to said compressor is
modulated.
3. In a system serially including a compressor, a discharge line, a
condenser, an expansion device, an evaporator and a suction line,
means for achieving capacity control comprising:
a solenoid valve in said suction line;
means for rapidly pulsing said solenoid valve whereby the rate of
flow in said suction line to said compressor is modulated;
a fluid path extending from a point intermediate said condenser and
said expansion device to said compressor at a location
corresponding to an intermediate point of compression in said
compressor;
an economizer circuit connected to said fluid path;
a solenoid valve in said economizer circuit; and
means for rapidly pulsing said solenoid valve in said economizer
circuit whereby the rate of economizer flow to said compressor is
modulated.
Description
BACKGROUND OF THE INVENTION
In a closed air conditioning or refrigeration system there are a
number of methods of unloading that can be employed. Commonly
assigned U.S. Pat. No. 4,938,666 discloses unloading one cylinder
of a bank by gas bypass and unloading an entire bank by suction
cutoff. Commonly assigned U.S. Pat. No. 4,938,029 discloses the
unloading of an entire stage of a compressor and the use of an
economizer. Commonly assigned U.S. Pat. No. 4,878,818 discloses the
use of a valved common port to provide communication with suction
for unloading or with discharge for V.sub.i control, where V.sub.i
is the discharge pressure to suction pressure ratio. In employing
these various methods, the valve structure is normally fully open,
fully closed, or the degree of valve opening is modulated so as to
remain at a certain fixed position. One problem associated with
these arrangements is that capacity can only be controlled in steps
or expensive motor driven modulation valves must be employed to fix
the valve opening at a certain position for capacity control.
SUMMARY OF THE INVENTION
Gradual compressor capacity can be achieved by rapidly cycling
solenoid valve(s) between fully open and fully closed positions.
The cycling solenoid valve(s) can be located in the compressor
suction line, the compressor economizer line and/or the compressor
bypass line which connects the economizer line to the suction line.
The percentage of time that a valve is open determines the degree
of modulation being achieved. However, because the cycling time is
so much shorter than the response time of the system, it is as
though the valve(s) are partially opened rather than being cycled
between their open and closed positions.
It is an object of this invention to provide continuous capacity
control.
It is another object of this invention to provide step control in
capacity modulation.
It is a further object of this invention to provide a less
expensive alternative to the use of variable speed compressors.
It is another object of this invention to provide a less expensive
alternative to a modulation valve. These objects, and others as
will become apparent hereinafter, are accomplished by the present
invention.
Basically, gradual or step control in capacity modulation of a
refrigeration circuit is achieved by rapidly cycling a solenoid
valve in the compressor suction line and/or the compressor
economizer line and/or bypass line.
BRIEF DESCRIPTION OF THE DRAWING
For a fuller understanding of the present invention, reference
should now be made to the following detailed description thereof
taken in conjunction with the accompanying drawing wherein.
The FIGURE is a schematic representation of an economized
refrigeration or air conditioning system employing the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the FIGURE, the numeral 12 generally designates a hermetic
compressor in a closed refrigeration or air conditioning system 10.
Starting with compressor 12, the system 10 serially includes
discharge line 14, condenser 16, line 18, expansion device 20,
evaporator 22, and suction line 24 completing the circuit. Line
18-1 branches off from line 18 and contains expansion device 30 and
connects with compressor 12 via port 12-1 at a location
corresponding to an intermediate point in the compression process.
Economizer heat exchanger 40 is located such that line 18-1,
downstream of expansion device 30, and line 18, upstream of
expansion device 20, are in heat exchange relationship. The
expansion devices 20 and 30 are labeled as electronic expansion
devices, EEV, and are illustrated as connected to microprocessor
100. In the case of expansion device 20, at least, it need not be
an EEV and might, for example, be a thermal expansion device, TEV.
What has been described so far is generally conventional. The
present invention provides bypass line 50 connecting lines 18-1 and
24 downstream of economizer heat exchanger 40 and evaporator 22,
respectively, and places solenoid valve 52 in line 50, solenoid
valve 54 in line 24 downstream of evaporator 22 and upstream of
line 50 and solenoid valve 56 in line 18-1 downstream of economizer
heat exchanger 40 and upstream of line 50. Solenoid valves 52, 54,
and 56 and EEV30 are all controlled by microprocessor 100
responsive to zone inputs. Where expansion device 20 is, as
illustrated, an EEV, it also is controlled by microprocessor
100.
In "normal" operation of system 10, valves 52 and 56 are closed and
hot high pressure refrigerant gas from compressor 12 is supplied
via line 14 to condenser 16 where the refrigerant gas condenses to
a liquid which is supplied via line 18 and idle economizer heat
exchanger 40 to EEV20. EEV20 causes a pressure drop and partial
flashing of the liquid refrigerant passing therethrough. The
liquid-vapor mixture of refrigerant is supplied to evaporator 22
where the liquid refrigerant evaporates to cool the required space
and the resultant gaseous refrigerant is supplied to compressor 12
via suction line 24 containing solenoid valve 54 to complete the
cycle.
The operation described above is conventional and capacity is
controlled through EEV20. Pursuant to the teachings of the present
invention solenoid valve 54 can be rapidly pulsed to control the
capacity of compressor 12. Since the pulsing will be more rapid
than the response time of the system 10, the system 10 responds as
though the valve 54 is partially open rather than being cycled
between its open and closed positions. Modulation is achieved by
controlling the percentage of the time that valve 54 is on and off.
To prevent a vacuum pump operation, the "off" position of valve 54
may need to permit a limited flow.
To increase capacity of system 10, economizer heat exchanger 40 is
employed. In economizer heat exchanger 40, lines 18 and 18-1 are in
heat exchange relationship. Solenoid valve 56 is open and solenoid
valve 52 closed and a portion of the liquid refrigerant in line 18
is directed into line 18-1 where EEV30 causes a pressure drop and a
partial flashing of the liquid refrigerant. The low pressure liquid
refrigerant passes into economizer heat exchanger 40 where the
refrigerant in line 18-1 extracts heat from the refrigerant in line
18 causing it to cool further and thereby provide an increased
cooling effect in evaporator 22. The refrigerant in line 18-1
passing through economizer heat exchanger 40 is supplied to
compressor 12 via port 12-1 under the control of valve 56 which is,
in turn, controlled by microprocessor 100. Line 18-1 delivers
refrigerant gas to a trapped volume at an intermediate stage of
compression in the compressor 12, as is conventional. However,
according to the teachings of the present invention the economizer
flow in line 18-1 and, as such, system capacity is controlled by
rapidly cycling valve 56 to modulate the amount of economizer flow
to an intermediate stage of compression in compressor 12. To lower
the capacity of system 10, bypass line solenoid valve 52 is
employed. In this arrangement, valve 56 is closed, and gas at
intermediate pressure is bypassed from compressor 12 via port 12-1,
line 18-1 and line 50 into suction line 24. The amount of bypassed
gas and, as such, the system capacity is varied by rapidly cycling
valve 52. Thus port 12-1 is used as both an economizer port and a
bypass or unloading port.
From the foregoing, it should be clear that the rapid cycling of
valves 52, 54 and 56, individually, allows for various forms of
capacity control with the amount of time a particular valve is on
relative to the time that it is off determining the degree of
modulation of capacity. The frequency of modulation for typical
systems can range from 0.1 to 100 seconds.
Although preferred embodiments of the present invention have been
illustrated and described, other changes will occur to those
skilled in the art. It is therefore intended that the scope of the
present invention is to be limited only by the scope of the
appended claims.
* * * * *